Therefore, no pinholes allowed.Plywood can rot from a pinhole.
I think what Jacques was saying is to use a denser foam core than Divinycel, if you want to use a foam core. If plywood, just make sure to use a BS1088 rated marine ply. I have no clue what's available in Split, but here we can often choose between Meranti and Okume marine plywood, both very good for boat building with epoxy and fiberglass.